The figure below illustrates schematically the different ways in which a given earth-system component is integrated in a monitoring and forecasting system. Let us take as an example the ocean and sea-ice components. After several years of development targeting seasonal forecast production, these components are now included in the ECMWF analysis and forecasting system, which provides a sound track record of improved forecast quality and operational feasibility. The prognostic ocean and sea-ice components are now deemed mature enough to be included in the next generation of C3S reanalyses. They are initialised via data assimilation using different observational data sets, and the interactions between ocean-atmosphere and sea-ice are represented during the forecast, resulting in increased skill of the seasonal forecasts and providing additional products on marine variables and sea-ice outlooks for user exploitation. The treatment of the chemical, biological and human-induced variations is perhaps less mature for modelling, or the cost is considered prohibitive, and therefore are traditionally treated as boundary conditions. Temporal variations of these fields are not well represented in current reanalyses and seasonal forecast, leading to suboptimal estimation and forecast of climate anomalies and extreme events. A natural evolution of the C3S services is to improve the temporal representation of these so-called boundary conditions, by exploiting recent concerted efforts on observational dataset as well as modelling developments.

Following this hierarchical line, CONFESS will facilitate the transition from Tier-1 to Tier-2 of vegetation and land use by harmonisation of state-of-the-art observational data sets delivered by the COPERNICUS Services – C3S and CGLS – to consistently represent, for the first time in C3S reanalysis and seasonal forecasting systems, the temporal variations of these components. It will improve the temporal variations of aerosols within Tier-2 by merging the CMIP6 radiative forcing with CAMS, in the first ever attempt to blend the forcing datasets used in climate integrations with those delivered by COPERNICUS Services. CONFESS will also explore the feasibility of transitioning between Tier-2 and Tier-3 for vegetation, volcanic aerosols and biomass burning. CONFESS will evaluate the performance of all these developments on multi-year simulations and seasonal re-forecasts. Both developments and evaluation reports will contribute to maintaining the highest level of quality and confidence on the information delivered by the next phase of C3S.